This invention relates to photographic cameras, and more particularly to a film transport driving and braking system in a camera with a long length film magazine.
Many film transport driving and braking systems which have found their uses in combination with a camera and a long length film magazine provide a means for electrically or mechanically controlling synchronized intermittent operations of two separate driving means, one of which is connected to the film advancing means including a sprocket in the camera, and the other of which is connected to the take up spool in the magazine, whereby the sprocket and the take up spool are driven for rotation in a period of time between the successive exposures. In application to a particular photography where a number of exposures have to be continuously made at a high frequency, various problems have been encountered by the above mentioned systems. For example, the reliability of the electrical control means is rapidly decreased as the frequency of exposures increases. On the other hand, in the case of the mechanical control means, it is made more difficult to establish the predetermined synchronization between the operations of the two separate driving means with a sufficiently high accuracy, thereby resulting in an increase of tension exerted on the film between the sprocket and the take up spool, and formation of a slack of loose film therebetween. Such an increased tension will cause residual movement of the film during exposure, or damage the film, while such a film slack tends to engage with the take up spool in the camera body so that the film transport control is made impossible.
In addition to the above mentioned drawbacks, there is another drawback that the diameter of the film coil on the take up spool is increased as the film is transported from the supply to the take up spool, thereby the increased inertia of the take up spool moves the film through a distance equal to the difference between the longitudinal lengths of the sprocket tooth and the perforation of the film, when the sprocket is stopped. As a result, the probability of recording indistinct images on the film is increased when the shutter is actuated just after the transmission of a driving torque to the take up spool is terminated.